查询词典 laser

The plasma ignition threshold of metal is got through experimental and numerical study. The vapour and plasma ignition times of the target are got based on the equation of heat conduction and cascade model. We suppose that the plasma is ignited when generations of new electrons are born in vapour generation time. The influence of temperature on the thermodynamics and optics parameters of material also have been considered in the model. The resulting theory has good agreement with the experiment and overseas report. A blade method to measure the laser spot is given in this paper with validation and error analysis. The plasma threshold of metals in atmosphere and water ambients both are diagnosed with the light deflection and piezoelectric transducer. A Q-switched pulsed Nd:YAG laser operating at infrared (1064nm), visible(532nm) and ultraviolet (355nm) wavelengths has been used. Al、Fe、Cu are used as targets and get a similar results with both method. Theoretical and experimental analyses are applied on the influence of wavelength on the threshold have been done, both of which have shown that the plasma threshold of metals decrease as the laser wavelength increases; The plasma threshold of metals are higher in water than in air and the pressure of the shock wave in water is five times higher than in air .

从热传导方程和雪崩电离机制出发，假设当电子增值210倍时，考虑了温度对材料热力学和光学参数的影响时，得到了气化和等离子体点燃的时间，利用该模型进行计算得到的结果与国内外报道及自行通过实验测得的阈值基本一致；提出了利用刀刃法测量激光光斑面积的方法，并通过实验进行了验证和误差分析；利用光偏转装置和压电换能器分别对空气和水中金属等离子体点燃阈值进行了实验诊断，激光器均为调Q－YAG激光器（波长1064nm，532nm，355nm，脉宽10ns），靶材分别为Al、Fe和Cu，两种测试方法得到的等离子体点燃阈值基本一致；本文从实验和理论计算两个方面讨论了波长对等离子体点燃阈值的影响，均得到了等离子体点燃阈值随著波长的增加而减小的结论；对空气中和水中不同环境下金属等离子体的点燃阈值进行了比较研究，得到了金属在水中的等离子体点燃阈值比空气中的大，且水中产生的冲击波的压强是空气中的5倍左右的结论。

Section 1 discusses the advantages of medical film printer and USB, and put forward one elementary design scheme of the system. The principle of laser printer and the holistic design scheme of system are presented detailedly in Section 2, while Section 3 expounds the technology of USB. Section 4 discusses design scheme of transfer system of the laser printer - includes the development of USB device and CPLD. The test of holistic laser printer and effect picture of medical image are presented in Section5. In the end, a review of this system and some bugs are put forwards at present.

本文主要分为六个部分，第一部分讨论了医用胶片打印机和USB总线技术的特点和发展趋势，并提出了系统的初步设计方案和研究意义；第二部分描述了医用激光胶片打印机的背景、工作原理和系统的各个组成部分；第三部分描述了通用串行总线2.0版(USB2.0)的通信原理；第四部分详细介绍了打印机数据传输系统的设计——包括USB设备的开发和CPLD的硬件和软件设计，并对这个传输系统的性能进行了分析；第五部分介绍了整个打印机的测试结果和实际打印医学影像的效果图；最后对本文做出总结并提出了不足之处和参考价值。

If the content of SiH〓 kept constant, the laser energy value of threshold that decomposed SiH〓 increased linearly at first, but when the gas flux exceeded 100ml/min, the laser energy value of threshold increased slowly because the coaxial Ar could not"suppress"the reaction flame which leaded to radial dilation of reaction gases and increasing the effective absorption to laser energy.

在反应气体中SiH〓含量不变的情况下，随着反应气体流量的逐渐增加，可以引发硅烷分解的激光能量阈值一开始成线性增加，当流量大于100ml/min以后，由于同轴Ar不能有效的&压住&反应焰，导致反应气体的径向扩张，增加了对激光能量的有效吸收面积，因此激光能量阈值的增加减缓。

Q-switched laser pulses can remove most tattoos effectively, with a low risk of scarring. Cosmetic tattoos, especially those with flesh-colored, red, tan or white inks, should be approached with caution when attempting removal by high-energy short-pulse laser, because of the possibility of laser-induced irreversible darkening.

Q开关雷射可以有效治疗刺青，而且结癖的危险性很低，化妆性刺青特别是肤色、红色、白色，在用高能量短脉冲雷射处理时需特别小心，因为会造成镇可逆的颜色变黑。

The results show that laser-arc welding can achieve full penetration by single-path butt jointing through appropriate parameters; Y shape groove with 8 mm truncated edge can enhance the penetration ability of laser-arc hybrid welding. Low welding speed is good for penetration, however the limitation still exists for hick plates joint. Gap is significant factor of penetration when work pieces is large thickness. The hardness of thick plates joint shows that there is big difference in mold of vertical thermal cycle using laser-arc hybrid welding.

结果表明：通过激光功率等焊接规范匹配，激光-电弧复合焊接能实现20 mm厚板的全熔透单道对接；钝边为8 mm的Y形坡口有助于提高厚板激光-电弧复合焊缝熔透能力；降低焊接速度有利于提高熔深能力；工件厚度较大时，装配间隙对焊缝熔深能力的影响较为显著；接头硬度表明厚板激光复合焊焊缝纵向热循环模式存在较大差异。

At high powers the nonlinear part of the index of refraction becomes important and causes a higher index of refraction in the center of the laser beam where the laser is brighter than at the edges causing a feedback that focuses the laser even more.

在高权力，非线性部分的折射率变得很重要的原因和较高的折射率为中心的激光束，在激光亮度比是在边缘，造成了反馈，重点激光甚至更多。

To decrease or eliminate the laser beam drift is the key to the high accurate laser measurement,especially the laser alignment technique.

寻求减少或消除激光光线漂移对测量影响的方法与技术，是高精度激光测量，特别是激光准直测量获得成功的关键。

Laser beam micro process ; 355nm UV DPSS Laser ; Telecentric Scan Lenes ; Micro hole array ; Laser drilling probe card guide sheet.

激光精细加工； 355nm紫外固体激光；远心扫描物镜；微孔列阵

Rotating laser ; laser levellers ; laser for autocontrol.

激光扫平仪；激光平地机；激光自动控制

Laser-based metrology and grating-based metrology are two main ultra-precision tools of dimension measurement. However, very few research work has been done on grating-based nanometrology compared with laser-based nanometrology till now because many people, including some grating researchers and specialists, hold the idea that the accuracy of grating-based measurement is lower than the laser's and can only reach micrometre or sub-micrometre level. They consider that it is unfeasible to get nanometer-scale accuracy using grating-based sensors.

激光技术和光栅技术是毫米级以上量程的精密几何量测量的两种最主要手段，目前，用激光进行纳米测量的研究已经很多，但光栅纳米测量技术的研究却很少；很多人，包括很多光栅研究者和测量专家，都认为，光栅测量的精度不如激光，其精度还只是停留在微米量级上，用光栅来进行更高精度的测量以至纳米测量是难以实现的。

This one mode pays close attention to network credence foundation of the businessman very much.

这一模式非常关注商人的网络信用基础。

Cell morphology of bacterial ghost of Pasteurella multocida was observed by scanning electron microscopy and inactivation ratio was estimated by CFU analysi.

扫描电镜观察多杀性巴氏杆菌细菌幽灵和菌落形成单位评价遗传灭活率。